Essay on Diversity and Distribution of Eucalyptus

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Diversity and Distribution of Eucalyptus

Eucalyptus is a genus of hardwood evergreen forest trees, and is the most conspicuous element of Australian vegetation. Its members constitute 95 percent of the continent's forests and are the dominant trees of Australia's woodlands (Kelly 1969). It is an extremely diverse group, with approximately 500 named species and subspecies and nearly 200 described hybrid varieties (Blakely 1965). The genus is overwhelmingly endemic to the Australian mainland and Tasmania. Only seven species occur naturally outside the continent, mostly on the islands of Papua/New Guinea and the Indonisian island of Timor, and only two of these species are not represented on the Australian continent. Eucalyptus is
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Thus, in response to this great diversity in habitat, Eucalyptus has, through many generations, adapted and speciated to become one of the most diverse living groups on earth. The diversity of the genus lies not only in its shear number of species, but also in the various forms, features, and morphological characters it displays.

Because of its great range of habitation, the widespread Eucalyptus displays a variety of shapes and sizes. The Snow Gum (E. pauciflora), which must deal with the harsh conditions of high altitudes, takes the form of twisted, windswept shrubs, often barely reaching three feet in height (Kelly 1969). However, the Mountain Ash (E. regnans) of the wet, rich-loamed Victorian and Tasmanian forests, often exceeds heights of 320 feet, making it the tallest Australian species and the tallest hardwood in the world. Most forest species rarely attain heights of 150 feet, while woodland species generally do not exceed 80 feet but have a short, thick trunk with heavy limbs to support a broad, spreading crown. Sometimes the same species occurs in both forests and woodlands, assuming the form characteristic of the vegetative type in which it grows (Hall, Johnston, and Chippendale 1970). A number of species exhibit a shrub-like dwarf form in which several stems arise from a large, woody rootstock composed of stem tissue (called a lignotuber) imbedded in shallow soil.
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